Priming mix

ABSTRACT

An improved priming mix of the type including an initiator, fuel, and oxidizer, and pyrotechnic component. The improvement being the inclusion of between about 3% and about 20% propellant superfines, the superfines comprising particles less than 100 μm.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to prior provisional application Ser.No. 61/226,496, filed Jul. 17, 2009, the entire contents of which areincorporated herein by reference.

FIELD

The present disclosure relates to priming mixes or priming compounds,and in particular to priming mixes with improved sensitivity.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Priming mixes or priming compositions are used in ammunition cartridges,including both center fire and rim fire, shot shells, and loads forpower tools and power actuated devices to initiate the combustion of thepropellant in the cartridge or shell. The priming mix is disposed in apriming cup at the back of the cartridge or shell. Ignition of theprimer is initiated by the impact of a weapon's firing pin on the cup.This mechanical energy deforms the cup, compressing the priming mix andgenerating heat, causing the priming mix to ignite. The combustionproducts from the burning priming mix are directed (e.g., by flash holesin the base of the cartridge or shell) to the propellant in thecartridge or shell.

It is of course desirable that the priming mix be sensitive to impact sothat it can initiate the combustion of the propellant, however,sensitivity in the context of priming mixes is more than merereactivity, rather it means more consistent performance for a givenimpact. Merely increasing the reactivity of the priming mix is neithersufficient nor desirable, because it could increase the incidence ofaccidental firing of the cartridge or shell. Instead, improvedsensitivity of priming mixes is measured by the compression of the rangeof heights from 100% fire to 100% misfire while maintaining the later atan established safe level, in a industry standard test called drop test,wherein the test was done by dropping weight on the composition fromstandard heights, and recording the number of times that the priming mixignites versus the number of times the priming mix does not at eachheight. What improves a priming mix versus what merely makes the primingmix more reactive is neither readily apparent, nor predictable.

A typical modern priming mix contains a primary explosive—a chemicalcompound which is impact sensitive. This primary explosive in almost allcases must be modified because it is too powerful or its velocity ofdetonation is too high. The modification is accomplished by the additionof other chemical ingredients which may be fuels, oxidizers,propellants, sensitizers, and other agents.

For example, since World War II it has been common to base priming mixeson lead styphnate, with various modifiers including secondaryexplosives, such as TNT, TNR, sensitizers, such as tetrazene, fines,such as double based propellant and PETN, fuels, such as aluminum,calcium, silicide and antimony sulfide, and oxidizers, such as bariumnitrate and potassium nitrate. More recently, efforts have been made toreduce the use of lead and other heavy metals in priming mixes, and thuspriming mixes based upon alternative primary explosives, such asdiazodinitrophenol (dinol or DDNP) or potassium dinitrobenzofuroxan(KDNBF), are increasingly common.

There is a continuing search for improved priming mixes with an improvedbalance sensitivity, stability, and other desirable properties.

SUMMARY

Generally, embodiments of the present invention provide a priming mixwith improved sensitivity. In accordance with a preferred embodiment, animproved priming mix of the type including an initiator, fuel, andoxidizer, and pyrotechnic component is provided. The improvement beingthat the composition comprises between about 3% and about 20% propellantsuperfines, and more preferably, between about 5% and about 8%superfines. It is believed that the superfines act as a fast fuel thatbridges the reaction between the primary explosive and the pyrotechnicmixture (i.e. the fuel and oxidizers) more reliably than theconventional fines due to its larger surface area. These superfines arepreferably through −140 mesh, and more preferably through −250 mesh.Preferably all of the particles have a diameter less than about 100 μm,and preferably at least 80% of the particles have diameters less thanabout 80 μm, and at least 50% of the particles have diameters less thanabout 40 μm. In one embodiment, these superfines have a median diameterof between about 23 μm and about 28 μm.

In another aspect, the superfines have a surface area of at least 2000cm² per cm³ of bulk material, and more preferably at least 3500 cm² percm³ of bulk material. Preferably at least 10% and more preferably atleast 50% of the total surface area of the superfines is from particlesof 26 μm or less, and at least 80% and more preferably 90% of the totalsurface area of the superfines is from particles of 40 μm or less.

In at least some embodiments, the average aspect ratio (longestdimension/shortest dimension) of the particles comprising the superfinesis less than 2.

The superfines can be a single-base propellant, a double-basepropellant, a triple-base propellant, or a mixture or composite ofsingle-base, double-base, and/or triple-base propellants.

While propellant fines have been used in priming mixes in the past (see,e.g., U.S. Pat. Nos. 4,963,201, 5,466,315, 5,417,160, 5,547,528,5,610,367, and 5,831,208), these fines have typically been finelydivided propellant made up of nitrocellulose and nitroglycerin (e.g. 60%nitrocellulose and 40% nitroglycerin). However these “fines” havetypically been an order of magnitude coarser that the superfines used inaccordance with the principles of this invention. Conventional finesrange in small particle sizes from about from 0.011 inch to 0.018 inch(280 μm to 460 μm) in contrast with the superfines, which the inventorhas discovered improved the sensitivity of priming mixes withoutadversely affecting reactivity.

Embodiments of the priming mix thus provide improved sensitivity whilemaintaining shelf life, reactivity, and safety.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a graph showing the particle size distribution of thepropellant superfines used with the preferred embodiments of thisinvention.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Embodiments of the present invention provide improved priming mixes ofthe type including an initiator, a fuel, an oxidizer, and a pyrotechniccomponent. According to the principles of this invention, theimprovement comprises between about 3% and about 20%, and morepreferably between about 5% and about 8%, propellant superfines in thepriming mix. These superfines are particles of a propellant that arepreferably less than 100 μm or −140 mesh.

In accordance with one aspect of the invention, the particles comprisingthe superfines have a median diameter of between about 20 μm and about30 μm, and more preferably between about 23 μm and about 28 μm.

In accordance with another aspect of the invention, the superfines havea surface area of at least 2000 cm² per cm³ of bulk material, and morepreferably at least 3500 cm² per cm³ of bulk material.

In accordance with another aspect of this invention, wherein at least10% and more preferably at least 50% of the total surface area of thesuperfines is from particles of 26 μm or less, and at least 80% and morepreferably 90% of the total surface area of the superfines is fromparticles of 40 μm or less.

In accordance with another aspect of this invention, the particlescomprising the superfines have an average aspect ratio (greatestdimension/smallest dimension) of less than 2. This is different fromfines conventionally in use which were often elongate and stringy.

In accordance with another aspect of this invention, the superfinescomprise particles less than about 100 μm, at least at least 80% of theparticles are less than about 80 μm; and at least 50% of the particlesare less than about 40 μm.

The particle size distribution of the superfines is illustrated inFIG. 1. The solid lines indicate the particle size distribution (leftscale), and the corresponding dashed line indicates cumulative surfacearea (right scale). In FIG. 1, A indicates one type of superfinessuitable for use in the embodiments of the invention; B and C indicatesconventional fines; and D indicates PETN.

The superfines can be of a single-base propellant, a double basepropellant, or a composite of single base and double base propellants.

Example 1

In a first preferred embodiment, a priming mix is made with from 30% to40% lead styphenate, 2% to 6% tetrazene, 0% to 6% PETN, 3% to 8%superfines; 2% to 5% aluminum, and 35% to 55% Ba(NO₃)₂. Morespecifically, an exemplary priming mix was made with about 35% leadstyphenate, about 5% tetrazene, about 3% PETN, about 5% propellantsuperfines, about 3% aluminum, and about 50% Ba(NO₃)₂.

More specifically, an exemplary composition of a priming mix and acontrol of the compositions shown in Table 1 were prepared, and testedin three sets of steel die drop tests. The results of which are reportedin Table 2.

As shown in Table 2, the performance of the exemplary composition issuperior at 5″, where there was at least one misfire out of fifty forthe control in each set compared to no misfire for the exemplarycomposition; at 4″, where there was at least eight and as many aseighteen misfires out of fifty for the control in each set, compared toa maximum of four misfires out of fifty for the exemplary composition;and at 3″, where the control had between 38 and 40 misfires out offifty, compared to between 23 and 28 misfires out of fifty for theexemplary composition. However, the exemplary composition stillmaintained an adequate safe level of sensitivity with no more than 2fires out of 50 at 2″ and no fire out of 50 at 1″. The exemplarycomposition also demonstrated better performance in the 10″ off-centerfiring pin strike with equal or less misfires than control,

TABLE 1 Exemplary Composition Control Lead Styphanate 35  40  Tetrazene4 4 PETN 3 5 Superfines 5 0 Aluminum 3 3 Barium Nitrate 50  48 

TABLE 2 # of misfires out of 50 Sample H S H + 4S H − 2S 7″ 6″ 5″ 4″ 3″2″ 1″ 10″ o.c. Steel Die Drop Test Results Set #1 by Primer QV N = 100Control 3.44 0.68 6.14 2.09 0 1 8 38 50 14 Example 3.04 0.64 5.60 1.76 02 27 48 50 2 Steel Die Drop Test Results Set #2 by Primer QV N = 50Control 3.56 0.86 6.99 1.84 0 3 14 36 50 2 Example 2.92 0.57 5.20 1.78 023 48 50 0 Steel Die Drop Test Results Set #3 by Primer QV N = 50Control 3.68 0.77 6.75 2.15 0 1 18 40 50 0 Example 3.14 0.62 5.64 1.89 04 28 50 0 1 o.c. stands for off-centerIn other preferred embodiments, primer compositions can comprise betweenabout 30% and about 45%, and more preferably between about 35% and about42%, of a dinitrobenzofuroxan salt, such potassium dinitrobenzofuroxan(KDNBF); between about 4% and about 6% tetrazene; between about 5% and15% superfines; between about 7% and 15% fuel, such as boron (B) or ironsulfide (ferrous sulfide) (FeS) or antimony sulfide (Sb₂S₃); and 30% to41% of an oxidizer, such as potassium nitrate (KNO₃), barium nitrateBa(NO₃)_(2;) or manganese peroxide MnO₂.

Example 2

A primer composition was prepared with the following composition:

-   -   35% KDNBF    -   4% Tetrazene    -   5% superfines    -   15% iron sulfide (ferrous sulfide) FeS    -   41% Potassium Nitrate KNO₃

Example 3

A primer composition was prepared with the following composition:

-   -   42% KDNBF    -   6% Tetrazene    -   8% superfines    -   7% Boron    -   37% Potassium Nitrate KNO₃

Example 4

A primer composition was prepared with the following composition:

-   -   42% KDNBF    -   6% Tetrazene    -   8% superfines    -   7% Boron    -   37% Barium Nitrate Ba(NO₃)₂

Example 5

A primer composition was prepared with the following composition:

-   -   35% KDNBF    -   4% Tetrazene    -   5% superfines    -   15% Antimony Sulfide (Sb₂S₃)    -   41% Potassium Nitrate KNO₃

Example 6

A primer composition was prepared with the following composition:

-   -   35% KDNBF    -   5% Tetrazene    -   15% superfines    -   15% iron sulfide (ferrous sulfide) FeS    -   30% Manganese peroxide MnO₂

1. An improved priming mix of the type including an initiator, fuel, andoxidizer, and pyrotechnic component, the improvement comprising betweenabout 3% and about 20% propellant superfines, the superfines comprisingparticles less than 100 μm.
 2. The improved priming mix according toclaim 1, comprising between about 5% and about 8% superfines.
 3. Theimproved priming mix according to claim 2 wherein the superfines have amedian diameter of between about 20 μm and about 30μ.
 4. The improvedpriming mix according to claim 3 wherein the superfines have a mediandiameter of between about 23 μm and about 28μ.
 5. The improved primingmix according to claim 2 wherein the superfines have a surface area ofat least 2000 cm² per cm³ of bulk material.
 6. The improved priming mixaccording to claim 5 wherein the superfines have a surface area of atleast 3500 cm² per cm³ of bulk material.
 7. The improved priming mixaccording to claim 5 wherein at least 10% of the total surface area ofthe superfines is from particles of 10 μm or less.
 8. The improvedpriming mix according to claim 7 wherein at least 33% of the totalsurface area of the superfines is from particles of 10 μm or less
 9. Theimproved priming mix according to claim 5 wherein at least 80% of thetotal surface area of the superfines is from particles of 30 μm or less.10. The improved priming mix according to claim 1, wherein the particlesof the superfines have an aspect ratio (greatest dimension/smallestdimension) of less than
 2. 11. The improved priming mix according toclaim 1 wherein the superfines are −450 mesh.
 12. The improved primingmix according to claim 1 wherein at least 80% of the particles are lessthan about 80 μm.
 13. The improved priming mix according to claim 12wherein at least 50% of the particles are less than about 40 μm.
 14. Theimproved priming mix according to claim 1 wherein the superfinescomprise superfines of a single-base propellant.
 15. The improvedpriming mix according to claim 1 wherein the superfines comprisesuperfines of a double-base propellant.
 16. The improved priming mixaccording to claim 1 wherein the superfines comprise superfines of atriple-base propellant.
 17. The improved priming mix according to claim1 wherein the superfines comprise superfines of at least two ofsingle-base, double-base, and triple-base propellants.
 18. A priming mixcomprising: from 30% to 40% lead styphenate, from 2% to 6% tetrazenefrom 0% to 6% PETN from 3% to 8% superfines; from 2% to 5% aluminum; andfrom 35% to 55% Ba(NO₃)₂. More specifically, an exemplary priming mixwas made with about 35% lead styphenate, about 5% tetrazene, about 3%PSTN, about 5% propellant superfines, about 3% aluminum, and about 50%Ba(NO₃)₂.
 19. A primer composition, comprising: 35% KDNBF; 4% Tetrazene;5% superfines; 15% iron sulfide (ferrous sulfide) FeS; and 41% PotassiumNitrate KNO₃.
 20. A primer composition, comprising: 42% KDNBF 6%Tetrazene 8% superfines 7% Boron; and 37% Potassium Nitrate KNO₃.
 21. Aprimer composition, comprising: 42% KDNBF; 6% Tetrazene; 8% superfines;7% Boron; and 37% Barium Nitrate Ba(NO₃)₂.
 22. A primer composition,comprising: 35% KDNBF; 4% Tetrazene; 5% superfines; 15% Antimony Sulfide(Sb₂S₃); and 41% Potassium Nitrate KNO₃.
 23. A primer composition,compirising: 35% KDNBF; 5% Tetrazene; 15% superfines; 15% iron sulfide(ferrous sulfide) FeS; and 30% Manganese peroxide MnO₂.